1. Technical Field of the Invention
The present invention relates to a starter for starting engines and its starting circuit, and in particular, to a starter having a system of pushing a pinion gear in the direction of an anti-motor side by using a shift lever driven by an electromagnetic switch.
2. Description of the Related Art
As disclosed in Japanese Patent No. 3478211, there is a starter for starting an engine with a conventional type of technology having a motor that generates a torque by energizing an armature and an electromagnetic switch that opens and closes a main point of contact provided in a motor circuit for energizing the motor with a current from a battery. There is provided a shift lever that is driven by using magnetic force generated by a switch coil of the electromagnetic switch and pushes a pinion gear and a clutch in the direction of an anti-motor side via a plunger and the shift lever.
Since this starter has a structure that the pinion gear and the clutch move together as a unit and a mass of a movable body is large, therefore it is necessary to increase the power of magnetic force. For that reason, there is adopted the electromagnetic switch having two coils for the switch coil, one for attracting and another for holding the plunger.
In the electromagnetic switch with two coils, the power of attraction is increased by energizing both the attracting coil and the holding coil, and reduces a combined resistance of the switch coil that increases an operation current. After the plunger is attracted and the main point of contact is closed, the attracting coil will become short-circuited by the main point of contact, and will be held at the state where the plunger is attracted only by magnetic force that the holding coil generates. Therefore, the attracting coil is energized only for a short time until the main point of contact is closed.
However, since the operating current for energizing the switch coil is large (about 40 amperes) for the electromagnetic switch with two coils, the operating current cannot be controlled directly by a switch with an ECU (electronic control unit).
Then, as shown in FIG. 6, a starter starting circuit 160 that controls an exciting current of a starter relay 140 by ECU is known. The starter relay 140 is arranged between a terminal 120 (generally called a 50 terminal) for energizing the switch coils (the attracting coil 100 and the holding coil 110) 150 and an ignition switch (it is hereafter called the IG switch 130).
Since the above-mentioned starter has the structure that the pinion gear and the clutch move together as the unit so and the mass of the movable body is large, it is inevitably necessary to increase the power of magnetic force (attracting force).
That is, the electromagnetic switch has the attracting coil 100 and the holding coil 110 and when attracting the plunger, energizing both the attracting coil 100 and the holding coil 110 that reduces the combined resistance of both the coils 100 and 110 increases the operating current.
Further, if the plunger is attracted and the main point of contact is closed, the attracting coil 100 will be short-circuited by the main point of contact, and will be held at the state where a plunger is attracted only by the magnetic force that the holding coil 110 generates. Therefore, the attracting coil 100 is energized only for a short time until the main point of contact is closed.
However, it is necessary to connect the attracting coil to the motor circuit for the electromagnetic switch with two coils, i.e., the attracting coil 100 and the holding coil 110. To be more specific, a connecting terminal is attached to an M terminal bolt fixed to a contact point cover of the electromagnetic switch, and an end of the attracting coil 100 is connected to the connecting terminal by welding etc.
With this composition, the number of parts increases, and a process for attaching the connecting terminal to the M terminal bolt and a process for connecting the end of the attracting coil 100 to the connecting terminal (welding) is also required, thus the cost would rise.
Further, since it is necessary to form the switching circuit 170 for energizing the terminal 120 for energization via the starter relay 140, and the relay circuit 180 for controlling the exciting current of the starter relay 140 by the ECU 150 in the above-mentioned starting circuit 160, the circuit composition becomes complicated and causes the cost to rise as a vehicles system.
Furthermore, it is necessary to constitute the IG switch 130 in two lines in order to connect the switching circuit 170 and the relay circuit 180, thus the IG switch 130 becomes complicated and expensive.